Since the early 70s, standard modular plug/receptacles have become a standard arrangement for connecting telephones to subscriber lines in the United States. Most people are now familiar with the modular plug, for example, of the type shown in U.S. Pat. Nos. 3,761,869 and 3,860,316. While there are several forms of the standard plug, the RJ11 type is probably the one with which most telephone subscribers are familiar.
Also, the last decade has seen a tremendous growth in the use of computers in industrialized countries throughout the world. Improvements in integrated circuit technology have led to a continuing decline in the price of computers. When the home or small business computers of today are compared with the computers of 10 to 15 year ago, it becomes apparent that the price of equivalent computing power has dropped approximately two orders of magnitude in a relatively short span of time.
The great proliferation of computers has led to a corresponding proliferation in the number of modems used in the United States and throughout the world. As is known to those skilled in the art, and most users of computers, modems (a contraction for modulator/demodulator) are devices which convert digital signals from a computer or terminal into a modulated signal appropriate for transmitting over telephone lines. Most modems for use in home computers use a modulation technique which is appropriate for the transmission of data within the relatively narrow passband of a standard, unconditioned, telephone line such as that normally found in the home.
As modular plugs/receptacles have become standard connection devices for connecting customer equipment to telephone lines, standard modular receptacles are normally found on modems being manufactured today for use in the United States.
Several very popular small computers in use today have a hardware architecture by which peripheral devices are connected to expansion slots on the mother board of the computer, as opposed to serial or parallel output ports being provided to the user. The expansion slot architecture allows a great deal of flexibility in the design of peripheral devices which can be connected to such computers. Additionally, the use of expansion slots allows the use of standard card sizes for the circuit boards upon which peripherals are constructed. A number of peripherals or expansion devices may be inserted into the expansion slots and the normal cover for the computer can be replaced. This arrangement allows the user to expand the capabilities of the computer without a corresponding expansion of the number of boxes and cables lying about at the computer installation site.
In the marketing of many small computers, a trade-off is necessary between the physical size of the computer and the number of expansion slots made available to the user. Users desire more and more expansion slots but, at the same time, there is a need to keep the size of the computer manageable. This, coupled with additional advances in circuit density through LSI and VLSI techniques, has led to designs in which expansion slots are relatively close together in many popular small computers. The close spacing of expansion slots results in a requirement that the profile of components placed on the circuit board be kept to a minimum. As used herein, the term profile refers to the physical height above the component side of a circuit board.
A confluence of all of the factors mentioned above has led to a great popularity of modems which are constructed on a single circuit board for insertion into an expansion slot of a small computer. A modular receptacle for connecting the modem to the telephone line is provided on the circuit board and is normally accessible through a back panel segment provided on the peripheral card.
As expansion slots are moved closer together, and less clearance is available between peripheral cards to be plugged into expansion slots, it has been found by the inventor of the present invention that available modular receptacles were too high for use in certain applications. In other words, the use of prior art modular receptacles on a circuit board modem designed to be plugged into an expansion slot was not practical, because the profile of the prior art modular receptacles was too high, and the user would be unable to insert another peripheral device into an adjacent expansion slot.
The particular application which led to the creation of the present invention was the slight narrowing of the back panel space which resulted from a design modification of the popular IBM personal computer to the IBM XT personal computer. However, the trend noted above is common throughout the industry, and the present invention will find applications in many other devices requiring low profile modular receptacles.
Naturally, the size of the opening required for acceptance of a standard modular plug places a lower limit on the profile that a printed circuit board mounted modular plug may have. However, it was discovered by the inventor of the present invention that the prior art did not provide a modular receptacle, that could be used for circuit board mounting, which effectively minimized the profile of the receptacle above the component side of the board. Thus there is a need in the art for an inexpensive modular receptacle which may be mounted on a printed circuit board which effectively minimizes the profile of the receptacle assembly above the plane of the board.